Report from ISMRM: MRA outperforms DSA for calf and foot arterial imaging

Despite shortcomings, contrast-enhanced MR angiography prevailed over digital subtraction angiography often enough in a head-to-head trial to become the modality of choice for investigations of suspected infrapopliteal occlusive disease at New York-Weill Cornell Medical Center.

Dr. Honglei Zhang, a radiologist at Weill, laid out the rationale for revisions to her department's policy at the International Society for Magnetic Resonance in Medicine meeting in Miami. Her study of 52 patients produced almost identical results for 2D projection MRA performed on a 1.5T scanner and DSA exams for the popliteal arteries. MRA was less robust for detecting occlusive arterial disease in the feet.

The overall sensitive and specificity of MRA to significant stenosis were 84% and 95%, respectively, in the calf and 79% and 71% in the foot. For arterial occlusion, the sensitivity and specificity of MRA rose to 89% and 95%, respectively, in the calf and 79% and 86% in the foot.

"In the calf, MRA tends to undergrade the severity, but in the foot, the possibility of undergrading and overgrading is nearly identical," Zhang said.

A reexamination of the 105 instances in which DSA and MRA disagreed found the differences in physician interpretation in 43 segments came from borderline lesions that could easily be graded either way, she said. In 22 segments, the reviewers decided MRA was more likely to be correct than DSA. DSA image quality was poor in three of those instances and suffered inadequate x-ray contrast opacification in the rest.

"This indicates that DSA is not perfect as a gold standard, and the real accuracy of MRA may be higher than was shown here," Zhang said.

The accuracy of MRA, especially in smaller distal vessels, may improve as better acquisition techniques such as 3D TRICKS and VIPR and better reconstruction techniques are introduced, she said.